Journal of Bone and Mineral Research最新文献

Calcium supplementation before exercise attenuates the decrease in serum calcium and increase in PTH and bone resorption. This study investigated the effect of calcium supplementation on calcium and bone metabolism during load carriage in women. Forty-eight women completed two load carriage sessions (load carriage 1 n = 48; load carriage 2 n = 40) (12.8 km in 120 min carrying 20 kg) 60 min after consuming either 1000 mg calcium (Calcium) or nothing (Control) in a randomised order. Pre- and post-exercise urine samples were analysed for calcium isotope ratio (δ44/42Ca). Fasted blood samples were taken before (pre-exercise), during (0, 20, 40, 60, 80, 100, 120 min), and after (+15, +30, +60, +90 min) exercise and analysed for markers of calcium and bone metabolism. There was no effect of load carriage or supplementation on urine δ44/42Ca (P≥.110). Serum δ44/42Ca did not change with load carriage in Control (P=.617) but increased in Calcium (P=.003) and was higher at 120 min in Calcium vs Control (P=.018). Ionised calcium (iCa) decreased from pre-exercise to all exercise time-points (P<.001); iCa was higher in Calcium than Control throughout (P<.001). PTH increased from pre-exercise to 120 min in Control (P<.001) but decreased from pre-exercise to all time-points in Calcium (P<.001). PTH was higher in Control than Calcium from 0 to +90 min (P<.001). βCTX decreased from pre-exercise to 20 to +15 min in Control (P≤.004); βCTX decreased from pre-exercise to 0 to +90 min in Calcium (P<.001). βCTX was lower in Calcium than Control from 20 to +90 min (P≤.036). A 1000 mg calcium supplement before load carriage promotes bone calcium balance and prevents disruptions to bone and calcium homeostasis.

We previously documented successful resolution of skeletal and dental disease in the infantile and late-onset murine models of hypophosphatasia (HPP), with a single injection of an adeno-associated serotype 8 vector encoding mineral-targeted TNAP (AAV8-TNAP-D10). Here, we conducted dosing studies in both HPP mouse models. A single escalating dose from 4x108 up to 4x1010 (vg/b) was intramuscularly injected into 4-day-old Alpl-/- mice (an infantile HPP model) and a single dose from 4x106 up to 4x109 (vg/b) was administered to 8-week-old AlplPrx1/Prx1 mice (a late-onset HPP model). Wild-type littermates were used as controls. Serum alkaline phosphatase activity was increased, and PPi levels were decreased in a dose-dependent manner in both the Alpl-/- and AlplPrx1/Prx1 models. Radiographic and μCT analysis of long bones of female and male Alpl-/- mice showed full correction of skeletal phenotype at 4x1010 vg/b. We observed full correction of the bone phenotype at 4x108 and 4x109 in female AlplPrx1/Prx1 mice, but bones remained hypomineralized with the 4x106 and 4x107 (vg/b) doses after 70 days of treatment. We observed skeletal improvements using the 4x109 (vg/b) dose, but the phenotype was not fully corrected in male AlplPrx1/Prx1. Immunohistochemistry using anti-TNAP and anti-D10 antibodies showed high immunolocalization in the femurs of female AlplPrx1/Prx1 mice, while D10 immunolocalization was high in the liver of male AlplPrx1/Prx1 mice at a dose of 4x109 (vg/b). This sex-dependent difference was not seen in the infantile HPP model. A serum proteome analysis showed enhanced inflammatory pathways in treated AlplPrx1/Prx1 males compared to treated female mice. We also found a few areas of ectopic calcification in soft organs at the highest tested dose of 4x1010 (vg/b) in Alpl-/- or 4x109 (vg/b) in the AlplPrx1/Prx1 model. This pre-clinical study will inform the design of clinical trials to develop gene therapy in early-onset and late-onset HPP patients.

Early increases in bone turnover markers (BTMs) in response to anabolic therapy correlate with 18-month bone mineral density (BMD) increases in postmenopausal women with osteoporosis; however, this relationship has not been assessed in men. In this analysis, the correlation between changes from baseline in fasting intact serum procollagen type I N propeptide (PINP) and serum carboxy-terminal cross-linking telopeptide of type I collagen (CTX) at 1, 3, 6, and 12 months and percent increase from baseline in BMD at 12 months in men from the randomized phase 3 ATOM study (NCT03512262) were evaluated using Pearson's correlation coefficients. The uncoupling index (UI), a measure of the balance between markers of bone formation (PINP) and bone resorption (CTX), with positive UI favoring bone formation, was calculated. Results in men were compared to 12-month results for women from the ACTIVE study using the z score test after Fisher's Z transformation. In abaloparatide-treated men, PINP increases at 1 month (r = 0.485), 3 months (r = 0.614), 6 months (r = 0.632), and 12 months (r = 0.521) were highly correlated (P<.0001) with 12-month lumbar spine BMD increases. The mean UI for abaloparatide-treated men was greater than placebo as early as 1 month (2.26 versus -0.25). At month 3, the mean UI for men was greater (1.32) than for women (0.88) (P<.001). There was a significant correlation between 3-month UI and lumbar spine BMD at 12 months in both men (r = 0.453; P<.001) and women (r = 0.252; P<.01); UI at months 6 and 12 were also significantly correlated with 12-month lumbar spine BMD in men and women, but the correlation was stronger in men than women. These data support that early changes in BTMs in men treated with abaloparatide are associated with subsequent changes in BMD similar to what has been reported in women. Trial registration: clinicaltrials.gov Identifier NCT03512262.

Vertebral fracture assessment (VFA) images from bone density machines enable the automated machine learning assessment of abdominal aortic calcification (ML-AAC), a marker of cardiovascular disease (CVD) risk. The objective of this study was to describe the risk of a major adverse cardiovascular event (MACE, from linked health records) in patients attending routine bone mineral density (BMD) testing and meeting specific criteria based on age, BMD, height loss, or glucocorticoid use have a VFA in the Manitoba Bone Mineral Density Registry. The cohort included 10 250 individuals (mean 75.5 years, 94% women without CVD) with VFA (February 2010 to March 2017) were included. ML-AAC24 scores were categorized (low <2; moderate 2- < 6; high ≥6). Over follow-up (mean 3.9 years), 1265 people (12.3%) experienced a MACE. Among those with low, moderate, and high ML-AAC24, MACE rates per 1000 person-years were 18.4 (95% CI 16.4-20.5), 34.1 (95% CI 30.9-37.4), and 55.6 (95% CI 50.8-60.1), respectively. A similar gradient was observed after stratifying by age and sex. Incidence rate ratios (IRRs) for low vs. moderate and high groups were 1.9 (95% CI 1.6-2.2) and 3.0 (95% CI 2.6-3.5), respectively. In those most likely to benefit from pharmaceutical intervention (<80 years, not on statins), MACE rates among those with low, moderate and high ML-AAC24 were 13.5 (95% CI 11.5-15.8), 26.0 (95% CI 22.1-30.3) and 44.1 (95% CI 37.0-52.0). Corresponding IRRs for low vs moderate 1.9 (95% CI 1.5-2.4) and high ML-AAC24 was 3.3 (95% CI 2.6-4.1]), respectively. In routine osteoporosis screening, individuals with moderate and high ML-AAC24 had substantially greater MACE rates compared to those with low ML-AAC24. Consequently, AAC detection during osteoporosis screening (especially in women) may guide intensification of preventative cardiovascular strategies.

Type 1 diabetes (T1D) is associated with an increased risk of hip fracture beyond what can be explained by reduced bone mineral density, possibly due to changes in bone material from accumulation of advanced glycation end-products (AGEs) and altered matrix composition, though data from human cortical bone in T1D are limited. The objective of this study was to evaluate cortical bone material behavior in T1D by examining specimens from cadaveric femora from older adults with long-duration T1D (≥50 yr; n = 20) and age- and sex-matched nondiabetic controls (n = 14). Cortical bone was assessed by mechanical testing (4-point bending, cyclic reference point indentation, impact microindentation), AGE quantification [total fluorescent AGEs, pentosidine, carboxymethyl lysine (CML)], and matrix composition via Raman spectroscopy. Cortical bone from older adults with T1D had diminished postyield toughness to fracture (-30%, p = .036), elevated levels of AGEs (pentosidine, +17%, p = .039), lower mineral crystallinity (-1.4%, p = .010), greater proline hydroxylation (+1.9%, p = .009), and reduced glycosaminoglycan (GAG) content (-1.3%, p < .03) compared to nondiabetics. In multiple regression models to predict cortical bone toughness, cortical tissue mineral density, CML, and Raman spectroscopic measures of enzymatic collagen crosslinks and GAG content remained highly significant predictors of toughness, while diabetic status was no longer significant (adjusted R2 > 0.60, p < .001). Thus, the impairment of cortical bone to absorb energy following long-duration T1D is well explained by AGE accumulation and modifications to the bone matrix. These results provide novel insight into the pathogenesis of skeletal fragility in individuals with T1D.

Achieving bone union remains a significant clinical dilemma. The use of osteoinductive agents, specifically bone morphogenetic proteins (BMPs), has gained wide attention. However, multiple side effects, including increased incidence of cancer, have renewed interest in investigating alternatives that provide safer, yet effective bone regeneration. Here we demonstrate the robust bone healing capabilities of the main megakaryocyte (MK) growth factor, thrombopoietin (TPO), and second-generation TPO agents using multiple animal models, including mice, rats, and pigs. This bone healing activity is shown in two fracture models (critical-sized defect [CSD] and closed fracture) and with local or systemic administration. Our transcriptomic analyses, cellular studies, and protein arrays demonstrate that TPO enhances multiple cellular processes important to fracture healing, particularly angiogenesis, which is required for bone union. Finally, the therapeutic potential of thrombopoietic agents is high since they are used in the clinic for other indications (eg, thrombocytopenia) with established safety profiles and act upon a narrowly defined population of cells.

Pregnancy and lactation-associated osteoporosis (PLO) is a rare presentation of early-onset osteoporosis characterized by low trauma and spontaneous fractures during late pregnancy/lactation. Herein, we report areal BMD (aBMD) by DXA and volumetric BMD (vBMD), microarchitecture, and strength at the distal radius and tibia by HR-pQCT in 59 women with PLO-in comparison to both healthy premenopausal controls (n = 28) and premenopausal women with idiopathic osteoporotic fractures not associated with pregnancy/lactation (non-PLO IOP; n = 50). Women with PLO (aged 34 ± 6 yr) had a more severe clinical presentation than non-PLO IOP: 80% had vertebral and 92% had multiple fractures (p<.001). They had lower DXA aBMD at all sites vs Controls (all p<.001) and non-PLO IOP (all p<.05). By HR-pQCT, PLO had deficits in all radial/tibial density and most microarchitecture parameters and lower bone strength than controls (all p<.001). Compared to non-PLO IOP, PLO had lower total and trabecular density at radius and tibia (all p ≤ .01) and significant deficits in trabecular microstructure and cortical thickness at the radius only. We studied PLO subgroups with clinical factors potentially related to bone physiology: Within PLO, women with vertebral fractures had lower spine aBMD and higher tibial cortical porosity but were otherwise structurally similar to the nonvertebral group. Those with prior heparin exposure had larger bone size and trabecular area, and those with renal stones had smaller bone size and lower 1/3 radius aBMD. We also compared groups based on postpartum timing: Recent PLO (n = 25) evaluated ≤12 M postpartum, before expected recovery of pregnancy/lactation bone loss, had significantly lower aBMD than distant PLO (n = 34) evaluated >12 M postpartum. However, radial/tibial HR-pQCT measures did not differ, suggesting pre-existing and/or persistent structural deficits. This structural study increases our mechanistic understanding of the severe bone fragility presentation that characterizes PLO and also highlights areas of potential mechanistic heterogeneity that require additional investigation.

Osteogenesis imperfecta (OI) constitutes a family of bone fragility disorders characterized by both genetic and clinical heterogeneity. Several different mouse models reproduce the classic features of OI, and the most commonly studied carry either a spontaneous or genetically induced pathogenic variant in the Col1a1 or Col1a2 gene. When OI is caused by primary alterations of type I collagen, it represents a systemic connective tissue disease that, in addition to the skeleton, also affects several extra-skeletal tissues and organs, such as skin, teeth, lung, heart, and others, where the altered type I collagen is also expressed. Currently, existing mouse models harbor a disease-causing genetic variant in all tissues and do not allow assessing the primary vs secondary consequences of the mutation on a specific organ/system. Here, we describe the generation of the first conditional knock-in allele for Col1a1 that can express a severe OI-causing glycine substitution (p.Gly1146Arg) in the triple helical region of α1(I) but only after Cre-driven recombination in the tissue of choice. We called this new dominant allele Col1a1G1146R-Floxed/+ and introduced it into the murine model. We describe its validation by crossing mice carrying this allele with EIIA-Cre expressing mice and showing that offspring with the recombined allele reproduce the classic features of a severe form of OI. The new mouse model will be useful to study the tissue-specific impact of this severe mutation on organs, such as the lung, the heart, and others.

The ketogenic diet (KD) has demonstrated efficacy in ameliorating inflammation in rats with osteoarthritis (OA). However, the long-term safety of the KD and the underlying mechanism by which it delays OA remain unclear. We found that while long-term KD could ameliorate OA, it induced severe hepatic steatosis in mice. Consequently, we developed 2 versions of ketogenic-based diets: KD supplemented with vitamin D and intermittent KD. Both KD supplemented with vitamin D and intermittent KD effectively alleviated OA by significantly reducing the levels of inflammatory cytokines, cartilage loss, sensory nerve sprouting, and knee hyperalgesia without inducing hepatic steatosis. Furthermore, β-hydroxybutyrate (β-HB), a convenient energy carrier produced by adipocytes, could ameliorate OA without causing liver lesions. Mechanistically, β-HB enhanced chondrocyte autophagy and reduced apoptosis through the activation of Erb-B2 receptor tyrosine kinase 3 (ERBB3) signaling pathway; a pathway which was down-regulated in the articular chondrocytes from both OA patients and mice. Collectively, our findings highlighted the potential therapeutic value of β-HB and KD supplemented with vitamin D and intermittent KD approaches for managing OA.